Drives for press installation, presses or other manufacturing equipment often have energy requirements which are very variable. The drives which draw their energy via intermediate converters from an energy supply system. The different energy requirements of the various drives are superimposed establishing an overall energy requirement which varies with time. With the introduction of modern converter installations are increasingly capable to field energy taken out of the energy supply system at least partially back into the power supply system. For example, energy may be energy may be taken out of this energy supply system for accelerating a drive. However, when the drive is to be shut down again energy may be returned to the energy supply system. This increases the changes in the power requirements of machines and plants.
DE 198 211 59 A1, for example, discloses a deep draw press whose plunger is driven by servomotors via spindles. Also the drawing cushion is driven by servomotors via spindles. The various servomotors of the plunger are interconnected by elastic shafts. Also the servomotors of the drawing cushion are interconnected by electric shafts. Both groups of servomotors are controlled by a computer program.
The many different servomotors cause varying loads on the energy supply system. This is objectionable and disturbing when several machines operating in parallel are operating at peak loads at the same time and an incidental or systematic synchronization of the energy withdrawal phases occur at the same time for the various drives and possibly the energy is also returned from the various drives to the energy supply system at the same time.
This problem may occur, for example, in connection with the press disclosed in DE 10 2005 026 818 A1 wherein various electric drives for the main movement of the plunger and the additional movement of the workpiece transport elements are interconnected via energy storage devices and/or energy exchange modules.
If energy storage devices are provided, the energy storage devices are constantly charged and discharged particularly in connection with the periodic operation of the presses. The capacitors are, therefore, arranged in heat exchange with liquid-conducting spaces or conduits wherein the liquid takes up heat at one point and releases it again at another. In addition, a cooling system is provided on the basis of so-called heat pipes.
Rail vehicles require for each starting process a relatively large amount of energy while essentially the same large amount of energy becomes available during the braking procedure and is to be stored in the capacitor modules. However, starting and braking procedures occur with substantial time delay so that a good amount of time is available for conducting the waste heat away. The cooling medium, for example, de-ionized water has a high heat capacity and therefore can take up relatively large amounts of heat and store it for some time.
In press installations however, energy use and energy release change within seconds, in large component stage presses, for example, in a four or five seconds rhythm. With the same rhythms, the capacitors must be able to take up and release the energy so that they generate waste heat practically constantly. Therefore, a powerful cooling system is required, and it is the object of the present invention to provide such a highly effective cooling system.